Actuatable occupant restraint systems, such as air bags, for vehicles are well known in the art. The air bag has an associated, electrically actuatable ignitor, referred to as a squib. Such systems further include an inertia sensing device for measuring the deceleration of the vehicle. When the inertia sensing device is subjected to a crash acceleration greater than a predetermined value, the inertia sensing device closes an electrical switch causing an electric current of sufficient magnitude and duration to be passed through the squib to ignite the squib. The squib, when ignited, ignites a combustible gas generating composition and/or pierces a container of pressurized gas, which results in inflation of the air bag.
Many known inertia sensing devices used in actuatable occupant restraint systems are mechanical in nature. Still other known actuatable occupant restraint systems for vehicles include an electrical transducer or accelerometer for sensing vehicle deceleration. Systems using an accelerometer as a crash sensor further include a monitoring or evaluation circuit connected to the output of the accelerometer. The accelerometer provides an electrical signal having an electrical characteristic indicative of the vehicle's deceleration, i.e., crash acceleration. The accelerometer is connected to a controller, such as a microcomputer. The microcomputer performs a crash algorithm on the acceleration signal for the purpose of discriminating between deployment and non-deployment crash conditions. When a deployment crash event is determined to be occurring, the restraint is actuated, e.g., an air bag is deployed.
Many types of crash algorithms for discriminating between deployment and non-deployment crash events are known in the art. Algorithms are typically adapted to detect particular types of crash events for particular vehicle platforms.